The patient I gave blood for had a large facial tumor and they had started to need blood during the surgery. The operating room notified the lab, who then called me to see if I was available, and within the next few minutes I was lying in a bed next to the ICU ready to get my blood sucked out. Maggie, the phlebotomist, or vampire as she calls herself, stuck a giant needle in my arm and sat holding the bag while the blood drained into it. A little more informal than a usual blood bank.
My favorite part was that afterwards I got free Coke and Oreos. The only thing better would have been if they were fried Oreos, I miss those.